Electron ionization mass spectra of 3,4-disubstituted-1,2,4-oxa(thia) diazole-5(4H)-thione(ones). Substituent effects on the mass spectrometric rearrangement of 3-aryl-4-(p-tolyl)-1,2,4-oxadiazole-5(4H)-thiones to the corresponding oxo compounds

Pihlaja K., Agirbas H., Valtamo P.

JOURNAL OF MASS SPECTROMETRY, cilt.36, ss.754-759, 2001 (SCI İndekslerine Giren Dergi) identifier identifier identifier

  • Cilt numarası: 36 Konu: 7
  • Basım Tarihi: 2001
  • Doi Numarası: 10.1002/jms.171
  • Sayfa Sayıları: ss.754-759


The fragmentation behaviour of ten 3,4-disubstituted 1,2,4-oxadiazole-5(4H)-thiones and seven 3,4-disubstituted 1,2,4-thiadiazole-5(4H)-ones studied here confirmed the earlier observations about the partial rearrangement of the former after ionization into the latter before further fragmentation. In the case of eight 3-(substituted phenyl)-4-(p-tolyl)-1,2,4-oxadiazole-5(4H)-thiones the fragmentations reflecting the above-mentioned molecular ion rearrangement show a clear correlation on the substituent a values. The electron-withdrawing substituents destabilize the molecular ion, so higher amounts of the rearranged ion [(RNCO)-N-1](+.) are obtained, A good correlation of log[R1NCO](+) against sigma was obtained (r = 0.96). Only a satisfactory correlation prevailed for log([(RNCO)-N-1](+.)/[(RNCS)-N-1](+.)) against sigma (r = 0.87). Copyright (C) 2001 John Wiley & Sons, Ltd.